Electrode mounting support

ABSTRACT

In order to be able to change, without problems, the characteristic of an intended force measuring device (95, 107 through 123) provided on an electrode mounting support (7), having an electrode holder (81), according to the electrode (105) being used, the mounting support has a mounting part (75) movably fixed to a conveyor carriage (5) of a solder or welding apparatus. Thereon is guided an electrode holder (81) by a ball piston/sleeve arrangement (89, 87) and by an additional piston/cylinder arrangement (87 through 89) acting in cooperation with an exchangeable pressure spring (95) of known characteristic. An inductive displacement pickup, integrated into the second piston/cylinder arrangement, including induction coil (119, 121) is provided on the surface of the cylinder and a ferrite core (125) for cooperating therewith is mounted in the piston. Therefore, with the exchange of the electrodes (105), the changing force can also be corrected for without any adjustments, for example, for equal support pressure, by exchange of the spring (95) or by change of the complete head.

The present invention concerns an electrode mounting support for awelding or soldering apparatus, which includes a conveyor carriageincluding an electrode holder that is vertically movable with regard tothe electrode working area and has a force measurement device formeasuring the force between the electrode and a workpiece.

PRESENT STATE OF TECHNOLOGY

A welding installation is known from DE-OS No. 27 38 854 which includesa supply sled. This device is powered to move the conveyor carriage andalso includes an electrode holder; the latter also being movablelineally with respect to the supply sled. A spring arrangement, betweenthe electrode holder and supply sled, takes up the force between theelectrode and the workpiece. The electrode force from the relativedisplacement of the electrode holder and supply sled can be regulatedwith the aid of a dial control. With the aid of an adjusting element,the pretension of the spring can be adjusted between the supply sled andelectrode holder. This device has a major disadvantage in that differentelectrodes with different working areas (depending on their use) can beused, but with the changing of the electrodes, requirements for equalpressure have to be taken into account and the operator might take acorrespondingly altered reading or change the preloading of the spring.This necessitates relatively high skill requirements for the operator.

DESCRIPTION OF THE INVENTION

The aim of the present invention is to create an electrode mountingsupport of the above-mentioned type in which the electrodes can bechanged without any difficulties, and where the operator does not haveto consider the regulated force required for different electrodes. Thisis accomplished by the electrode mounting support being constructed as aremovable fixed head in relation to a conveyor carriage, with at leastone mounting part movably mounting the electrode mounting to support theconveyor carriage. A force measurement device is disposed between theholder and the mounting part. The force measurement device includes aspring element which can be exchanged by means of a removable supportpart mounted on the holder or mounting part. When the electrodes have tobe exchanged, the whole head with the force measurement device and aspecific spring can be exchanged, or in an alternate embodiment, atleast the spring element can be exchanged.

Preferably, the holder on the mounting part is guided lineally andvertically to the electrode working area. Therefore, with such a head,the electrodes are brought into contact without any rotational movementbeing imparted to the workpiece.

As a force measurement device, an intermediate holder and a mountingpart is preferably provided along with an inductive displacement pickupacting with a spring arrangement. With a raised electrode, the provisionof a spring element between the mounting portion and holder ensures thatthe holder is maintained in a floating condition with regard to themounting parts.

Especially for aperture welding electrodes, it is proposed that themounting part includes at least an intermediate holder which supports anelectrode holder whereby the intermediate holder can be regulated on themounting part parallel to the electrode working area, preferably throughlinear displacement. As a result, two parts are provided which aremovable in the desired direction relative to each other and on each anelectrode can be mounted whose distance can be adjusted by theintermediate holder. Preferably, a force measurement device is alsoplaced on the intermediate holder and electrode holder, especially whenit is necessary to specifically regulate the force at each electrode,such as with aperture welding electrodes. When two intermediate holdersare provided on the mounting part, which can be positioned symmetricallyin a direction parallel to the electrode working area by means of anadjusting element, displacing of the electrode symmetrically ispossible.

By the use of the mentioned inductive displacement pickup, the result isan extremely compact construction for a mounting support, since theholder, by means of at least one piston/cylinder arrangement, is guidedon the mounting part and the inductive displacement pickup is anintegral part thereof, preferably with an inductive coil on the cylinderwall and a magnet on the piston.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described with examples with the aid of the figures.Shown are:

FIG. 1, a cross-sectional view of an electrode mounting supportaccording to the invention,

FIG. 2, an end view of the electrode head of FIG. 1,

FIG. 3, a partial cross-sectional view of an electrode mounting supportfor aperture welding electrodes,

FIG. 4, an end view of the mounting support of FIG. 3,

FIG. 5, a front view of the electrode mounting support of FIG. 4,

FIG. 6, a view of an additional, improved variation of an electrodemounting support,

FIG. 7, a front view of the mounting support of FIG. 6,

FIG. 8, a schematic of a displacement pickup in a bridge circuit for theevaluation of position signals as produced on the electrode headsaccording t FIGS. 1 through 7,

FIG. 9, a schematic of an additional design variation of the bridgecircuit of FIG. 8,

FIG. 10, a graph of the amplitude of the transfer characteristic curveof a bridge according to FIG. 8 or 9, shown qualitatively,

FIG. 11, a graph of the qualitatively shown phase shift of the bridgeoutput signal according to FIGS. 8 and 9,

FIG. 12, a graph of the combination of a characteristic curve and thetransfer characteristic curve of a displacement pickup as shown, forexample, in FIGS. 7 and 8 for the construction of a power receivercharacteristic line as realized with the mounting supports according toFIGS. 1 through 7.

DESCRIPTION OF THE INDIVIDUAL FIGURES

In FIG. 1, an electrode mounting support 7 is shown. The mountingportion 75 includes an adjustable mounting device 79, which can betightened or loosened by means of a tightening screw 77, for themounting of the solder or welding device on a supply element or conveyorcarriage 5. An electrode holder 81 is mounted by a guide piston 85 whichis fastened in a bushing 83 that is formed on one end thereof with theother end thereof including roller bearings forming a ball piston 87which is movable in a cylinder 89, the latter being rigidly mounted tothe mounting portion 75. The guide piston 85 is lineally movable indirection P₂. The cylinder 89 includes threads 91 on the upper portionthereof which accommodate a removable screw 93 which serves as a cover.Between the screw 93 and the upper end of the ball piston 87 is disposeda pressure spring 95 whose displacement/force characteristic is known.An additional spring 97, a pull spring, is disposed in a chamber 101 andis fastened on one side thereof in a mounting support 99 and on theother side thereof to the holder portion 81. This pull spring 99supports the weight of the electrode holder 81 along with a clamped downelectrode 105 fixed in position by set screws 103.

An additional cylinder 107 is mounted on the mounting part 75. A guideanchor 111, disposed within the cylinder 107, slides in a coaxialbushing 109 which has an anchor piece on its lower portion, located in ahole 113, which is fastened to support the electrode holder 81. Ananchor piece 115, like the anchor 111 in the bushing 109, is guidedthrough the mounting part 75 in a correspondingly dimensioned lowerbushing 117. Between the outer wall of the bushing 109 and the innerwall of the cylinder 107 are disposed two coils 119 and 121, which areinserted in a center hole 123 of the anchor 111 and have disposedtherethrough a core 125, preferably of a ferrite material. As will bedescribed with the aid of FIGS. 8 and 12, the two coils 119 and 121 andthe core 125, which moves relative to the coils 119 and 121 as theelectrode holder 81 moves relative to the mounting part 75, form aninductive displacement pickup means, the electrical connections for thecoils 119 and 121 not being shown. Basically, the inductive value of thetwo coils are changed relative to each other through the displacement ofthe core 125. If, for example, the two coils are connected into aninductive measuring bridge, an indication is given of the relativeposition of the mounting part 75 and the carrier 81 and therefore theelectrode position.

By knowing the spring characteristic of the pressure spring 95, theresult is that pressure measurements can be made by the inductivedisplacement pickup means and the force F can be translated into thepressure which exists between the workpiece and the electrode 105.Therefore, an inexpensive and precise force or pressure measuring devicecan be realized on the head-shaped mounting support combined with theprovided guide.

In FIG. 3 there is shown an embodiment of a head including the alreadydescribed structure as shown in FIG. 1 but this embodiment is especiallymodified for aperture welding electrodes. In overview, the embodimentshown in FIG. 3 is configured for symmetrically adjustable aperturewelding electrodes as also shown in FIG. 4 and as shown in a front viewin FIG. 5. FIG. 3 also is representative of an embodiment forasymmetrically displaced aperture electrodes as further shown in FIG. 6and in a front view in FIG. 7.

A mounting part 123, again with a mounting support 127 and a fasteningscrew 125, has on both sides a pair of guide posts 129a, 129b, and 131a,131b, which are fixed perpendicular to the longitudinal axis of themounting part 123 and parallel to each other. The guide posts 131 and129 each slide into guide holes 133a, 133b, and 135a, 135b, each inpairs being disposed in the intermediate holder 137a and 137b. Theintermediate holders 137a and 137b are therefore supported with regardto the mounting portion 123 and can be lineally displaced in directionP₃. The adjustment of the two intermediate holders 137 is achieved bymeans of a dial 139, preferably with a planetary speed reduction, commonto micrometers, which drives the intermediate holder 137b by means of athreaded rod 141b in a shaft hole 143b whereby the threaded rod 141b isaxially fixed, but rotatable in the mounting part 123 and is supportedby support part 145. On the other side of the mounting part 123, thesupport part 145 is continued and cooperates with a threaded shaft 141a,which rests in a threaded hole 143a in the intermediate holder 137a. Forthe mirror image symmetrical operation of the two intermediate holders137 with regard to the middle surface E of the mounting part 123, thethreads between the threaded rod 141a/threaded hole 143a and thethreaded rod 141b/threaded hole 143b are cut in opposite turningdirections.

As can be seen from FIG. 3, additional guide posts 147 or 149 areprovided on both sides, above and below, the threaded rod 141a, 141b andrun in the correspondingly arranged guide holes in the intermediateholders 137a, 137b. Therefore, a guide with just enough clearance of theparts 137 and 123 is provided, the relative position of which can beselected with the aid of an adjusting head 139.

The two intermediate holders 137a, 137b each have an inductivedisplacement pickup constructed as previously described in regard to thedesigns of FIG. 1 as a whole, and are designated by 150a and 150b.Provided are a roller piston guide with a pressure spring, eachdesignated as a whole by 151a or 151b. On each intermediate holder 137aand 137b, there is provided an electrode holder constructed andsuspended, in the same manner as the similar elements represented inFIG. 1, as a whole designated by 153a or 153b. The pull springsuspension for the spring, similar to the spring 97 of FIG. 1 isdesignated by 156a or 156b. As can be seen from FIG. 3, an additionalcoil 155 can be provided so that the whole arrangement, as will behereinafter described with the aid of FIG. 9, acts as a differentialtransformer. Consequently the intermediate holders, with regard to themounting part 123, are symmetrically adjustable in direction P₃according to FIGS. 3, 4, and 5 and the electrode holders 153a or 153bare movable in direction P₂, independent of each other with regard tothe associated intermediate holders 137a.

With the aid of the two pressure spring arrangements 151a, 151b and thedisplacement pickups 150a, 150b, each associated with an intermediateholder and electrode holder and each being intended for measuringpressure developed by the associated intermediate holder and theassociated electrode holder, the support forces F₁,2 acting on each ofthe provided aperture electrodes is detected.

As shown in FIGS. 6 and 7, a second variation of an electrode head isillustrated, designed especially for aperture electrodes. A support part123', is provided and has only one intermediate holder 137b whereby, ascan be seen from this figure, the one electrode holder 153b is connectedwith the intermediate holder 137b in the same fashion as shown in FIGS.1 through 5. Since no second intermediate holder 137a is intendedaccording to FIG. 4, the second electrode holder 153c is displaced indirection P₂ and is mounted directly on support part 123'. With the aidof the adjusting head 139' and the threaded rod 141b, which engages athreaded sleeve 143b on the intermediate holder 137b, the intermediateholder is displaced in direction P₃ with regard to the mounting part123'.

Shown in FIG. 8 is the circuit arrangement provided to measure variationof the inductance of the two coils 119 and 121 as the core 125 movesaccording to FIG. 1. This arrangement can also be provided between theelectrode holder and intermediate holder or support part, according toFIGS. 3, 6, and 7. The two coils 119 and 121 are coupled in an inductivebridge with two additional fixed impedances Z₁ and Z₂. The bridge ispowered by an alternating voltage generator 160. The tap between the twocoils 119 and 121 is connected through an adjusting unit 163 with thetap between the two fixed impedances Z₁ and Z₂. Instead of directlysupplying the bridge by the alternating voltage generator it ispossible, according to FIG. 9, for example with the apparatus shown inFIG. 3, to connect the output signal of the alternating voltagegenerator 160 through a primary winding 155, in a transformer fashion,into the bridge by way of the coils 119, 121, and into Z₁ and Z₂ and theadjusting unit 163. In this case, the two coils 119 and 121 togetherwith the primary coil 155 act as differential transformer. In bothdesign variations, the adjusting unit 163 supplies a signal whichindicates the relative position between the core 125 and the two coils119 and 121, and since the coils are mounted on a support part or anintermediate holder, the adjusting unit supplies an output signal whichindicates the relative position in direction P₂ between at least oneelectrode holder and the mounting support.

Qualitatively shown in FIG. 10 is an amplitude curve U(s) of the outputsignal u(s) from the adjusting unit 163 which is generated as a functionof the displacement s of the core 125 with respect to the zero position0 shown in FIG. 8.

Shown in FIG. 11, qualitatively, is the phase shift φ (s) of U(s). Withthe detection of the momentary amplitude U(s) and the phase sign φ (s)of the mentioned output signal U(s), a definite indication of thementioned relative position is maintained, shown by a dotted line inFIG. 10.

Shown in FIG. 12 is the dependence of force F_(k) from the distance sbetween the electrode holder and the intermediate holder and thereforeindirectly between electrode holder and the mounting part or from theelectrode holder directly with regard to the mounting part. In bothcases s corresponds therefore to the relative position of electrode andmounting part. If the one electrode being looked at is at its restposition at s_(r), the described inductive displacement pickup suppliesan output signal according to U_(sr). When the electrode, by themovement of the mounting support, makes contact on a workpiece it willbe lifted with its electrode holder against the force of the pressurespring 95 shown in FIG. 1. The reaction force created by the spring 95follows the example curve shown in FIG. 12 by e. Thereby the outputsignal of the inductive displacement pickup decreases toward the 0value. Preferably, the pressure spring is adjusted such that when theelectrode goes back by a distance s_(r), the spring creates a presetpressure or the preset force F_(soll) predetermined for the workingradius. Therefore, the electrode arrives at its working position when,on the output of the adjusting unit 163, a zero signal as U_(Soll)appears as shown in FIG. 8 or 9. This output signal can be used as anadjusting value through the predetermined spring characteristic. Inorder to consider the different preset forces by the use of differentelectrodes, the springs will either be exchanged with the electrodes ordifferent heads will be used with the desired corresponding springs.

With the known displacement/force characteristic of the intended springson the described electrode heads and the provision of the describeddisplacement pickups, a preset displacement signal can be given.Therefore, for a pressure regulation between the intended electrodes andthe workpiece, the output signal of the displacement pickup is compared,as an adjustable value, with a preset value which corresponds to thepreset displacement and therefore with the preset pressure.

I claim:
 1. An electrode mounting support for a welding or solderingelectrode comprising:a conveyor carriage and an electrode mount, saidelectrode mount being linearly movably guided on said conveyor carriagerelative to an electrode working area; and force measuring meansincluding spring means and displacement pickup means, said spring meansand said displacement pickup means acting between said conveyor carriageand said electrode mount, said spring means including a spring cavitywherein a spring is mounted, and means for accessing said spring withinsaid cavity for replacement of said spring without affecting saiddisplacement pickup means, said spring means being mounted to exert aforce along a line of action displaced from the line of action of saiddisplacement pickup means.
 2. An electrode mounting support according toclaim 1, wherein said electrode mount is guided by at least two pistonssaid spring means being mounted at one end of one of said pistons andsaid displacement pickup means being mounted adjacent the second of saidpistons.
 3. An electrode mounting support according to claim 2, whereinsaid displacement pickup means comprises an induction coil disposedaround the second piston and a magnet core within the second piston. 4.An electrode mounting support according to claim 1 further comprisingsupporting second spring means between said conveyor carriage and saidelectrode mount to support said mount.
 5. A method for adjusting thework force acting between an electrode and a workpiece to accommodatedifferent electrode requirements in an apparatus which includes a springmeans for providing said force, and force measuring means includingdisplacement measuring means, said method comprising the stepsof:selecting a desired electrode for use; selecting a correspondingspring means for use, said spring means being predetermined as beingsuitable for providing a force appropriate for use in conjunction withsaid electrode; replacing a previously positioned electrode and springmeans with said selected electrode and said selected spring means andemploying the same in combination, employment of said selected springmeans causing said force measuring means to be calibrated to saidselected electrode.